After hunting through the site, it appears easy to add, but impossible to remove licenses without going through sales support (instant response with a human), who then transfer you to the "Cancellation Team" which are remarkably hard to find online and have not replied to previous attempts at cancellation.
This is my third try, and the wait has been ridiculous. After finally being connected to a member of their cancellation team, they are "reviewing my request" and 1-2 minutes (please stand by) has turned into 15+
This experience has been so bad (on top of many others), that I'm strongly considering moving our entire org to open source tools (aside from InDesign for the publications group, which our partners require).